package cn.phantom.juctest;

import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

@Slf4j(topic = "c.TestAqs")
public class TestAqs {
    public static void main(String[] args) {
        MyLock lock = new MyLock();
        new Thread(() -> {
            lock.lock();
            try {
                log.debug("locking...");
                try {
                    TimeUnit.SECONDS.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            } finally {
                log.debug("unlocking...");
                lock.unlock();
            }
        }, "t1").start();

        new Thread(() -> {
            lock.lock();
            try {
                log.debug("locking...");
            } finally {
                log.debug("unlocking...");
                lock.unlock();
            }
        }, "t2").start();
    }
}

// 自定义锁（不可重入锁）
class MyLock implements Lock {

    // 独占锁 同步器类
    class MySync extends AbstractQueuedSynchronizer {

        @Override
        protected boolean tryAcquire(int arg) { // 如果是可重入锁会用到arg
            if (compareAndSetState(0, 1)) {
                // 设置了锁，并设置owner为当前线程
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }

        @Override
        protected boolean tryRelease(int arg) {
            setExclusiveOwnerThread(null);
            setState(0);
            return true;
        }

        @Override // 是否持有独占锁
        protected boolean isHeldExclusively() {
            return getState() == 1;
        }

        public Condition newCondition() {
            return new ConditionObject();
        }
    }

    private MySync sync = new MySync();

    /**
     * 加锁，不成功进入阻塞队列
     */
    @Override
    public void lock() {
        sync.acquire(1); // 不能用tryAcquire，tryAcquire只会尝试一次
    }

    /**
     * 加锁，可打断
     */
    @Override
    public void lockInterruptibly() throws InterruptedException {
        sync.acquireInterruptibly(1);
    }

    /**
     * 尝试加锁（一次）
     * @return
     */
    @Override
    public boolean tryLock() {
        return sync.tryAcquire(1);
    }

    /**
     * 尝试加锁，带超时
     */
    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return sync.tryAcquireNanos(1, unit.toNanos(time));
    }

    /**
     * 解锁
     */
    @Override
    public void unlock() {
        sync.release(1);
    }

    /**
     * 创建条件变量
     */
    @Override
    public Condition newCondition() {
        return sync.newCondition();
    }
}
